The present invention relates to the field of electronic equipment and, in particular, to the circuit boards that are used within electronic equipment.
A printed circuit board (PCB) is a board upon which a layer of metallic traces are routed. PCBs are typically constructed of epoxy resin and copper, however, a variety of other materials may be used. As circuits increase in complexity, PCBs are being developed into multiple layer boards with each layer forming trace planes on the board. The routing traces of these layers may be soldered to integrated circuits and/or board connectors.
A pair of connectors may be used to connect two PCBs together. A typical connector pair includes a header and a receptacle, each including a plastic housing and multiple contact elements. The complementary formed header and receptacle fit together such that the electrical contacts of the header are aligned with the electrical contacts of the receptacle. In this manner, a connector pair completes an electrical circuit between two PCBs. The connector pair must fit and remain properly coupled such that an acceptable electrical connection is established.
PCBs are extensively used within electronic equipment, such as computer systems. Examples of PCBs include a motherboard, a daughterboard, a backplane, a midplane, etc. During manufacturing of a PCB, the board may assume a warped or non-planar configuration that may be the result of various manufacturing, handling, and installation problems. During some manufacturing processes such as soldering, the PCB and the components and connectors soldered thereon are subjected to high temperatures. These high temperatures may warp or bend the PCB to some extent.
Moreover, PCBs are typically manufactured very thin and, thus, suffer from a lack of structural stability. The thinness of a PCB may make the PCB vulnerable to deflection resulting from shock, vibration, and connector insertion loads that may damage or break the solder connections and/or loosen the connector pair couplings. For example, a PCB may be exposed to upwards of 96 lbs of insertion force depending on the size and type of connectors on the PCB. In addition, during use, thin PCBs may bend simply because of the weight placed on them, especially for larger size PCBs. As a result, the deflection of a PCB may reduce the reliability of electrical connections between connector pairs and/or circuits on the board.
One solution is to install a board stiffener to reduce the amount of board deflection. FIG. 1A illustrates a prior board stiffener that consists of a formed metal bar that has multiple tabs that are soldered to a PCB. FIG. 1B illustrates another fabricated metal stiffener that has multiple tabs that mount to a PCB. One problem with using such board stiffeners is that PCBs may have routing traces that are predominately located along the midpoint of the board and, thus, consume most of the available space in that area, as illustrated in FIG. 1C. This reduces the available connection points for structural support. In addition, the number and location of mounting holes for stiffeners may be limited due to the size of the connectors, as illustrated by FIG. 1D, as well as the internal trace routing of the PCB.
Yet another problem with formed metal stiffeners is that the use of pins to attach the stiffener to the PCB requires soldering. As previously mentioned, soldering subjects the board to high temperatures that may warp or bend the PCB to some extent. Furthermore, soldering stiffeners to boards adds manufacturing expense and complexity. Formed metal stiffeners may also have limited structural capability due to size limitation. In addition, the use of screws to attach the stiffener to the PCB may also result in problems such as lost screws in the chassis and/or impact damage to the PCB and/or PCB components from screwdrivers that slip off screw heads.
Another problem with using the board stiffeners of FIGS. 1A and 1B is that they may not provide enough structural support for connectors that are located at the periphery of a PCB. One solution is to install multiple elongate bars across the upper, middle, and bottom sections of a PCB. A problem with such a solution is that the use of multiple elongate bars adds considerable expense to manufacturing costs. Another problem is that the mounting of multiple elongate bars requires separate manufacturing steps which adds both considerable time and cost to the manufacture of electronic equipment containing PCBs with such stiffeners.